Hkmp5sd:
An interesting and unanswered, unanswerable question re Miller might be as follows. Given that Miller was NOT represented before USSC, and that therefore the government's position and claims went unquestioned, what might The Court have done had Miller been represented by counsel, which could well have brought up the fact that short barreled shotguns had been MILITARY ISSUE during WW1 and earlier, not to mention their use by the militray during what have been described as "the years between the wars".
The following has also been brought up, I believe. Given that your average bolt, lever or pump action rifle or shotgun was NOT an item of military issue, whereas such arms as the Browning Automatic Rifle and Thompson Sub-machinegun were, that the above mentioned "sporting arms" might lack constitutional protection, while possession of military issue small arms might benefit from constitutionally protected status. After all, militia weapons, while they might NOT include artillery pieces, could well includ such arms as were normally issued to the infantryman of the day. In 1939, such arms would include the BAR and the Thompson, as well as the Johnson Light Machinegun. I've NOT mentioned the Garand because that was simply a semi-automatic rifle. Today, a listing of individual weapons would certainly include various sub-machineguns such as the MP-5, as well as selective fire rifles such as the M-16, in it's various configurations.
If I remember correctly, one of the then sitting justices, McReynolds I think, offered something about arms normally issured to the individual soldier, this would exclude crew served weapons, being constitutiponally protected when possessed by individuals.
Anyhow, Miller was not represented before The Court, so all we are doing here is speculating, if you will, playing "what if" sort of games, which while perhaps interesting, do not solve current questions.
As to the D.C. law, which dates to 1976, the 200th anniversity of the country, local government bodies do all manner of dumb, questionable, perhaps even illegal things. This act was APPROVED by a majority of The Congress (House and Senate), as memory serves.